How to take the a rail journey from London to Luxembourg

The variations in journey time partially depend on the connecting time between the trains at Bruxelles Midi/Zuid station.
The quicker journey times are indicative of a transfer time between trains of around 20 minutes.

If you miss the connection in Bruxelles due to a delay on the Eurostar, your tickets will be valid on the next train on to Luxembourg; because seats cannot be reserved on the Bruxelles - Luxembourg trains.
There is 1 x train per hour daily between Bruxelles/Brussels and Luxembourg.

More information is available on our changing trains at Bruxelles-Midi station guide.

At St Pancras:

Eurostar is currently suggesting that Standard Class And Standard Premier ticket holders should be at the Eurostar departure area in St Pancras International 90 mins before departure; and that Business Premier ticket holders should be there 45-60mins prior to departure.

The departure gates will close 30 mins prior to departure for Standard Class And Standard Premier ticket holders; and 15 mins prior to departure for Business Premier ticket holders.

Our guide to taking a Eurostar from London is here.

Note that London is in a different time zone to mainland Europe, it is one hour behind; hence what can seem like a discrepancy between the journey time and the interval between the departure and arrival times.

Book early and save: Yes

Online bookings open: up to 330 days ahead of the travel date.

Seat reservations are mandatory on the Eurostar, so will be included when booking tickets, but they are not available on the train on to Luxembourg.

Eurostar does not sell tickets for London to Luxembourg journeys by train, but the cheapest option can be to book tickets Any Belgian Station tickets on Eurostar.com - and then on arrival at Bruxelles-Midi/Zuid station you can visit the SNCB International Tickets office and purchase a ticket that will be valid from the Belgian border on to Luxembourg.
Doing so can save more than €25.

When making the booking on Eurostar select any Belgian town other than Bruxellles as destination - so Antwerp or Gent etc.
The name of the specific location in Belgium won't be printed on the ticket - it will simply state that it is valid for travel on to 'any station in Belgium -including the final station in Belgium on the Bruxelles - Luxembourg route.

Regardless of what ticket(s) are booked, if you won't be reliant on taking the final train of the day on from Bruxelles to Luxembourg, if the Eurostar from London is delayed, you can hop on any subsequent onward departure.
Eurostar train's general ticket terms:

'Customers can exchange tickets for travel in Standard and Standard Premier class multiple times without paying an exchange fee, as long as tickets are exchanged 7 days or more before the departure time of their individual journey
Though if the new ticket option is more expensive the difference in price will need to be paid, but if it is cheaper the price difference won't be refunded.
But make the exchange within 7 days of the individual journey and an admin fee of £30 will need to be paid, along with the price difference
Tickets to travel in Standard and Standard Premier class are not refundable.
In contrast tickets to travel in Business Premier Class can be refunded and they can be exchanged to alternative departures without paying the admin fee, or the price difference'.
Eurostar's full ticket terms and conditions are here.

Using Rail Passes on Eurostar:

Rail pass users can now pay reservation fees to travel on Eurostar trains, in a similar manner to other international European high speed trains.

The new rail pass reservation fees are similar to the cheapest single journey ticket prices, but as those cheapest tickets can sell out quickly, it's likely that the rail pass reservation fees will save money.

You can purchase these online with no booking fees via B-Europe - or they ARE now available on the Eurostar website.
Booking in advance is recommended as it's not unknown for rail pass reservations on Eurostar services to sell out days or weeks in advance, there is evidently limited availability per departure.

You can obtain a rail pass reservations without paying a booking fee at Eurostar stations.
However, if you want to do this on the day of travel be prepared to be flexible re: the train you will take.

If you are a UK resident, your rail pass + reservation is only valid if you take a train from the UK on the first day that your pass is valid for - and a return to the UK on the final day that you will be using a pass.